Wet-spun yarns or other yarns requiring controlled heat treatment or immersion in various treating baths are often required to have a certain, controlled, amount of moisture included therein prior to the treatment. The feed for such yarns has often been provided from immersion in water but such is cumbersome and often leads to inconsistent results due to water carried on the exterior of the yarn filaments.
The feed for such yarns can, of course, be provided on-line from wet-spinning manufacture but, because the subsequent treatments are nearly always much slower than the spinning process, on-line wet yarn supply causes a serious fiber production bottleneck.
For some applications in the past, a creel for holding and supplying yarns from several yarn spool sources was used. Before the present invention, however, creels could not successfully be used to supply wet yarns because the amount of moisture on the supply yarns was not constant and that led to interrupted process operation and inconsistent product qualities. For optimum operation of such treatments using wet yarn supplied from creels, the yarn in the creel must be maintained at a constant, controlled, moisture level.
In the manufacture and/or subsequent processing of some yarns, it is necessary to control the moisture content of the yarn (MOY-Moisture On Yarn) to within a certain range. An example of such a process is the manufacture of precursor yarns to make high modulus para-aramid yarns such as those disclosed in European Patent Application 247889, published Dec. 2, 1987. In the manufacture of such yarns, water-swollen precursor yarns are subjected to heat treatment under tension to increase the modulus and maintain a high tenacity in the finished yarn. The maximum benefits of a process such as the one of that European Patent Application are obtained when the yarns are "never-dried", that is, when they are maintained at a controlled, relatively high, moisture content after spinning and prior to being subjected to further treatment. Another example of a process where a certain moisture content in wet feed yarn is important is a process wherein yarns are colored or treated by an imbibition process such as in British Patent 1,438,067. In such a process, it is desirable for precursor yarns to have a certain, controlled, MOY before being placed into the imbibition bath; and in the process of that reference, the wet-spun feed yarns are supplied from immersion.
Before the present invention, in fiber treatment operations subsequent to spooling of never-dried fibers where attempts were made to supply fiber from creels situated in the open, ambient, conditions of the manufacturing facility, the results were unsatisfactory. Packages or spools of fiber which were mounted on the creels were mounted with, generally, a proper and desired MOY, but during the wait for process startup and during the rather lengthy operation of the process, itself, moisture was lost from the several spools in unacceptably large amounts and the moisture was lost in an uneven way such that the fiber treatment operations were conducted on fibers which were too dry and which were of varying moisture content.